#include <stdio.h>
#include <stdint.h>
#include <math.h>
#include<string.h>
uint16_t binary_to_uint(const char *str) {
// Your logic here
int n = strlen(str);
int num = 0;
int j = 0;
for(int i=n-1;i>=0;i--){
num += (pow(2,j)*(str[i]-'0'));
j++;
}
return num;
}
int main() {
char bin[20];
scanf("%s", bin);
printf("%u", binary_to_uint(bin));
return 0;
}